The confinement of animals by various means extends back to prehistoric times. As man has developed more specialized needs and varieties of animals, the means for their care has also evolved.
The maintenance of domestic animals in racks of cages is of relatively recent origin. Techniques and apparatus have been primarily aimed at the needs of poultry, particularly chickens. For example, U.S. Pat Nos. 3,726,255 to Marr and 4,046,107 to Kuster disclose cages designed to prevent such problems as breast blisters, swollen hocks, and snagged toes and feet in caged poultry. The U.S. Pat. No. 3,726,255 teaches a method for preventing the breast and hock abrasions of chickens by the use of a resilient mat placed over the standard cage floor. The U.S. Pat. No. 4,046,107 teaches the use of a movable panel of small grid size placed over the regular floor of the cage to prevent the chickens feet from slipping through the cage.
A problem with both inserts is that the waste material no longer freely falls through the cage floor. In the case of the mat, resilient motion helps the material pass through the openings. In the design using a hard insert, the floor is bracketed so that the movement of the chicken pushes the two pieces together to help force the waste material through the smaller grid.
Developments over the last twenty to thirty years in science and industry has promoted the keeping of animals other than poultry in racks of cages. These animals are primarily small mammals such as rabbits, rats, hamsters, guinea pigs, and mice.
The majority of cages for these animals are of standard construction, with four sides, one of which is a door, a top, and a bottom which allows the waste material to pass through onto a collection pan. An example of such a cage where the panels disassemble for storage is U.S. Pat. No. 3,721,213 to Bruggeman.
Due to the distinctive demands of laboratory work, cages have been further specialized so that they provide for the animal's comfort, are easily cleaned and sterilized, and can be uniformly positioned on storage racks to provide the maximum number of cages in the available space while maintaining adequate ventilation and spacing necessary to prevent the spread of disease.
The most common way to prevent the spread of disease through contact of the animals while insuring adequate ventilation is to design the cage with an open or a solid top, three solid side walls, and an open grided front wall. The bottom must necessarily be an open grid to allow the waste material to pass onto the collection tray below. Open topped hanging cages that slide into brackets mounted on the underside of shelves on the racks have the advantage that they do not require doors since the underside of the shelf serves as a solid barrier (or top) for the animal cage and access to the cage is easily provided by sliding the cage out from the rack to expose the open top. This allows the food and water containers to be directly mounted on the front, open grided panel for maximum utilization of area at a minimum cost.
A drawback to these cages is that, due to economic considerations, they are constructed out of a single sheet of metal to which a grid is attached at the front and on the bottom. Not only do the cages not come apart for storage, but they can only be used for one variety of animal, for example a rat, and not another animal of a different size, for example a mouse. The mouse could escape through or be injured by the larger grid used for containing a rat, and the waste material of the larger animal, the rat, would not go through the smaller grid used for a mouse.
As a consequence, cages of each grid size must be inventoried so that the required cage size is available when needed. This is expensive because extra cages must be purchased and because the extra cages must be stored when not in use.
It is therefore a principal object of the present invention to provide a cage which is convertible for use with more than one variety or size of animal.
Another object of the invention is that the means of conversion not alter the size or ability of the cage to be cleaned and sterilized.
Yet another object of the present invention is that the means of conversion is simple, inexpensive, reliable and can be stored in a relatively small area.
A still further objective of the present invention is that it not be detrimental to the health and welfare of the caged animal.